Field of the Invention
Embodiments of the invention relate to a power supply apparatus and a display device including the same.
Discussion of the Related Art
Generally, power supply apparatuses rectify an alternating current (AC) voltage to convert into a direct current (DC) voltage, or boost or drop a DC voltage to a desired voltage, thereby supplying a desired DC voltage to various devices (for example, display devices, light emitting diodes (LEDs), etc.)
FIG. 1 is a diagram for describing a related art power supply apparatus.
Referring to FIG. 1, the related art power supply apparatus includes a voltage converter 10, which converts an input power Vin into a DC voltage having a higher voltage level than the input power Vin by using an inductor L, and a voltage stabilizer 20 that stabilizes an output voltage Vout output from the voltage converter 10.
The voltage converter 10 includes a first switching element SW1 that is connected between the inductor L and the voltage stabilizer 20, a second switching element SW2 that is connected between a ground node and a node which is disposed between the inductor L1 and the first switching element SW1, and a pulse width modulation (PWM) controller 12 that generates first and second PWM signals S1 and S2 with a feedback output voltage to control a switching operation of each of the first and second switching elements SW1 and SW2. The voltage converter 10 stores a current in the inductor L with the input power Vin according to the switching operations of the first and second switching elements SW1 and SW2 based on the first and second PWM signals S1 and S2 of the PWM controller 12, and adds the current, stored in the inductor L, to the input power Vin to output a DC voltage having a higher voltage level than the input power Vin.
The voltage stabilizer 20 includes a third switching element SW3, which is connected between an output terminal Pout and an intermediate terminal (or an intermediate node) Pmin which is supplied with the DC voltage from the voltage converter 10, and a low drop out (LDO) controller 22 that generates a third PWM signal S3 with the feedback output voltage to control a switching operation of the third switching element SW3. The voltage stabilizer 20 stabilizes an output voltage Vout output from the voltage converter 10 according to the switching operation of the third switching element SW3 based on the third PWM signal S3, and outputs the output voltage Vout to the output terminal Pout.
The voltage converter 10 and the voltage stabilizer 20 may be integrated into one integrated circuit (IC), and mounted on a printed circuit board (PCB). The PCB includes an input terminal Pin to which the input power Vin is applied, an intermediate terminal Pmin which is supplied with the DC voltage from the voltage converter 10, and the output terminal Pout. Here, each of capacitors C for removing ripple and/or noise is connected between the input terminal Pin, the intermediate terminal Pmin, the output terminal Pout and respective grounds.
In the related art power supply apparatus, when short circuit between the intermediate terminal Pmin and a ground occurs due to a foreign material such as dust, a potential of the intermediate terminal Pmin is 0 V. At this time, without the first switching element SW1 of the voltage converter 10 acting as an ideal switch, a closed circuit in which a current flows through an internal diode of the first switching element SW1 which is in a forward direction with respect to a direction of a current is formed, and thus, as illustrated in FIGS. 2 and 3, the potential Vmin of the intermediate terminal Pmin always is 0 V, whereby an overcurrent Iinput flows instantaneously. For this reason, the inductor L and the first switching element SW1 of the voltage converter 10 are damaged (or broken down).
For example, in an instance where the input power is 3.7 V, a DC resistance (DCR) of the inductor L is 0.3Ω, and a forward voltage (VF) of the first switching element SW1 is 0.7 V, a current of 10 A flows to the ground through the inductor L and the internal diode of the first switching element SW1 when the intermediate terminal Pmin is short-circuited, and thus, a current equal to or higher than a rated current flows in the inductor L and the first switching element SW1. For this reason, the IC is damaged, and due to a momentary overcurrent, the IC and the PCB are heated, causing firing.